If you filed for bankruptcy, you may qualify for exclusion of any taxable income on your 1099-C.
You can file your 2018 return, and if you receive a 1099-C later, you can Amend your 2018 return or include the 1099-C on your 2019 return (check the year shown on the 1099-C).
Click the link for a Guide to Cancelled Debt for more detailed information.